Programmable Read-Only Memory. Read-only memory which can be programmed by the user using a special hardware programmer.

Anemometer whicb measures wind speed by measuring the degree of cooling of a metal wire heated by an electric current. A type of cooling power anemometer.

The amount of sky covered or concealed by clouds or obscuring phenomena. It is reported in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky. The following classifications are used in aviation weather observat ...

Particle on which the freezing of water occurs.

Very small precipitation drops (diameters less than 0.5 mm) that appear to float with air currents while falling in an irregular path. Unlike fog droplets, drizzle falls to the ground.

The record or trace made by a microbarograph.

A unit of pressure which directly expresses the force exerted by the atmosphere. Equal to 1000 dynes/cm2 or 100 pascals.

An instrument for measuring the relative speed of a fluid. It consists of a concentric pipe arrangement in which the inner pipe is open at one end and the outer pipe is perforated and closed at both ends. Each pipe is connected to a manometer. The unit is ...

A class of rain gauge in which the level of the collected rain water is measured by the position of a float resting on the surface of the water.

Any horizontal wind velocity tangent to the contour line of a constant pressure surface (or to the isobar of a geopotential surface) at the point in question.

A unit of distance equal to 5280 feet. It is sometimes referred to as a land mile.

The lowest value of a measured quality at which a sensor meets its accuracy specification.

The time required for an instrument to registe 63.2% of a step change in the variable being measured.

The quantity to be measured (or modulated, or detected, or operated upon) which is received by an instrument. Thus, for a thermometer. temperature is the input quantity.

A seasonal wind of persistent direction, characterized by a pronounced change in direction between seasons.

variable audio-modulated radiosonde developed at the Bureau of Standards and used by the United States weather services.

The atmospheric pressure computed using station elevation as the reference datum level. Station pressure is usually the base value from which sea level pressure and altimeter setting are determined.

A device that allows a terminal or computer at one location to communicate with a terminal or computer at a distant location via wire or phone lines.

Root Mean Square. This notation is used frequently with error analysis. In that context, it is the square root of the arithmetic mean of the squares of the deviations of the individual calibration points from the theoretical or ideal response.

A faintly-colored circular arc similar to a rainbow but formed on fog layers containing drops whose diameters are 100 microns or less. Also called mistbow, white rainbow.